sig.c

   1 /* sig.c - interface for shell signal handlers and signal initialization. */
   2
   3 /* Copyright (C) 1994 Free Software Foundation, Inc.
   4
   5    This file is part of GNU Bash, the Bourne Again SHell.
   6
   7    Bash is free software; you can redistribute it and/or modify it under
   8    the terms of the GNU General Public License as published by the Free
   9    Software Foundation; either version 2, or (at your option) any later
  10    version.
  11
  12    Bash is distributed in the hope that it will be useful, but WITHOUT ANY
  13    WARRANTY; without even the implied warranty of MERCHANTABILITY or
  14    FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  15    for more details.
  16
  17    You should have received a copy of the GNU General Public License along
  18    with Bash; see the file COPYING.  If not, write to the Free Software
  19    Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
  20
  21 #include "config.h"
  22
  23 #include "bashtypes.h"
  24
  25 #if defined (HAVE_UNISTD_H)
  26 #  include <unistd.h>
  27 #endif
  28
  29 #include <stdio.h>
  30 #include <signal.h>
  31
  32 #include "shell.h"
  33 #if defined (JOB_CONTROL)
  34 #include "jobs.h"
  35 #endif /* JOB_CONTROL */
  36 #include "siglist.h"
  37 #include "sig.h"
  38 #include "trap.h"
  39
  40 #include "builtins/common.h"
  41
  42 #if defined (READLINE)
  43 #  include "bashline.h"
  44 #endif
  45
  46 #if defined (HISTORY)
  47 #  include "bashhist.h"
  48 #endif
  49
  50 extern int last_command_exit_value;
  51 extern int return_catch_flag;
  52 extern int loop_level, continuing, breaking;
  53 extern int parse_and_execute_level, shell_initialized;
  54 extern int interactive, interactive_shell, login_shell, startup_state;
  55
  56 /* Non-zero after SIGINT. */
  57 int interrupt_state;
  58
  59 /* The environment at the top-level R-E loop.  We use this in
  60    the case of error return. */
  61 procenv_t top_level;
  62
  63 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
  64 /* The signal masks that this shell runs with. */
  65 sigset_t top_level_mask;
  66 #endif /* JOB_CONTROL */
  67
  68 /* When non-zero, we throw_to_top_level (). */
  69 int interrupt_immediately = 0;
  70
  71 static void initialize_shell_signals ();
  72
  73 void
  74 initialize_signals ()
  75 {
  76   initialize_shell_signals ();
  77   initialize_job_signals ();
  78 #if !defined (HAVE_SYS_SIGLIST) && !defined (HAVE_STRSIGNAL)
  79   initialize_siglist ();
  80 #endif
  81 }
  82
  83 void
  84 reinitialize_signals ()
  85 {
  86   initialize_shell_signals (1);
  87   initialize_job_signals ();
  88 }
  89
  90 /* A structure describing a signal that terminates the shell if not
  91    caught.  The orig_handler member is present so children can reset
  92    these signals back to their original handlers. */
  93 struct termsig {
  94      int signum;
  95      SigHandler *orig_handler;
  96 };
  97
  98 #define NULL_HANDLER (SigHandler *)SIG_DFL
  99
 100 /* The list of signals that would terminate the shell if not caught.
 101    We catch them, but just so that we can write the history file,
 102    and so forth. */
 103 static struct termsig terminating_signals[] = {
 104 #ifdef SIGHUP
 105   SIGHUP, NULL_HANDLER,
 106 #endif
 107
 108 #ifdef SIGINT
 109   SIGINT, NULL_HANDLER,
 110 #endif
 111
 112 #ifdef SIGILL
 113   SIGILL, NULL_HANDLER,
 114 #endif
 115
 116 #ifdef SIGTRAP
 117   SIGTRAP, NULL_HANDLER,
 118 #endif
 119
 120 #ifdef SIGIOT
 121   SIGIOT, NULL_HANDLER,
 122 #endif
 123
 124 #ifdef SIGDANGER
 125   SIGDANGER, NULL_HANDLER,
 126 #endif
 127
 128 #ifdef SIGEMT
 129   SIGEMT, NULL_HANDLER,
 130 #endif
 131
 132 #ifdef SIGFPE
 133   SIGFPE, NULL_HANDLER,
 134 #endif
 135
 136 #ifdef SIGBUS
 137   SIGBUS, NULL_HANDLER,
 138 #endif
 139
 140 #ifdef SIGSEGV
 141   SIGSEGV, NULL_HANDLER,
 142 #endif
 143
 144 #ifdef SIGSYS
 145   SIGSYS, NULL_HANDLER,
 146 #endif
 147
 148 #ifdef SIGPIPE
 149   SIGPIPE, NULL_HANDLER,
 150 #endif
 151
 152 #ifdef SIGALRM
 153   SIGALRM, NULL_HANDLER,
 154 #endif
 155
 156 #ifdef SIGTERM
 157   SIGTERM, NULL_HANDLER,
 158 #endif
 159
 160 #ifdef SIGXCPU
 161   SIGXCPU, NULL_HANDLER,
 162 #endif
 163
 164 #ifdef SIGXFSZ
 165   SIGXFSZ, NULL_HANDLER,
 166 #endif
 167
 168 #ifdef SIGVTALRM
 169   SIGVTALRM, NULL_HANDLER,
 170 #endif
 171
 172 #ifdef SIGPROF
 173   SIGPROF, NULL_HANDLER,
 174 #endif
 175
 176 #ifdef SIGLOST
 177   SIGLOST, NULL_HANDLER,
 178 #endif
 179
 180 #ifdef SIGUSR1
 181   SIGUSR1, NULL_HANDLER,
 182 #endif
 183
 184 #ifdef SIGUSR2
 185   SIGUSR2, NULL_HANDLER,
 186 #endif
 187 };
 188
 189 #define TERMSIGS_LENGTH (sizeof (terminating_signals) / sizeof (struct termsig))
 190
 191 #define XSIG(x) (terminating_signals[x].signum)
 192 #define XHANDLER(x) (terminating_signals[x].orig_handler)
 193
 194 static int termsigs_initialized = 0;
 195
 196 /* Initialize signals that will terminate the shell to do some
 197    unwind protection.  For non-interactive shells, we only call
 198    this when a trap is defined for EXIT (0). */
 199 void
 200 initialize_terminating_signals ()
 201 {
 202   register int i;
 203 #if defined (HAVE_POSIX_SIGNALS)
 204   struct sigaction act, oact;
 205 #endif
 206
 207   if (termsigs_initialized)
 208     return;
 209
 210   /* The following code is to avoid an expensive call to
 211      set_signal_handler () for each terminating_signals.  Fortunately,
 212      this is possible in Posix.  Unfortunately, we have to call signal ()
 213      on non-Posix systems for each signal in terminating_signals. */
 214 #if defined (HAVE_POSIX_SIGNALS)
 215   act.sa_handler = termination_unwind_protect;
 216   act.sa_flags = 0;
 217   sigemptyset (&act.sa_mask);
 218   sigemptyset (&oact.sa_mask);
 219   for (i = 0; i < TERMSIGS_LENGTH; i++)
 220     sigaddset (&act.sa_mask, XSIG (i));
 221   for (i = 0; i < TERMSIGS_LENGTH; i++)
 222     {
 223       sigaction (XSIG (i), &act, &oact);
 224       XHANDLER(i) = oact.sa_handler;
 225       /* Don't do anything with signals that are ignored at shell entry
 226          if the shell is not interactive. */
 227       if (!interactive_shell && XHANDLER (i) == SIG_IGN)
 228         {
 229           sigaction (XSIG (i), &oact, &act);
 230           set_signal_ignored (XSIG (i));
 231         }
 232       if (XSIG (i) == SIGPROF && XHANDLER (i) != SIG_DFL && XHANDLER (i) != SIG_IGN)
 233         sigaction (XSIG (i), &oact, (struct sigaction *)NULL);
 234     }
 235
 236 #else /* !HAVE_POSIX_SIGNALS */
 237
 238   for (i = 0; i < TERMSIGS_LENGTH; i++)
 239     {
 240       XHANDLER(i) = signal (XSIG (i), termination_unwind_protect);
 241       /* Don't do anything with signals that are ignored at shell entry
 242          if the shell is not interactive. */
 243       if (!interactive_shell && XHANDLER (i) == SIG_IGN)
 244         {
 245           signal (XSIG (i), SIG_IGN);
 246           set_signal_ignored (XSIG (i));
 247         }
 248       if (XSIG (i) == SIGPROF && XHANDLER (i) != SIG_DFL && XHANDLER (i) != SIG_IGN)
 249         signal (XSIG (i), XHANDLER (i));
 250     }
 251
 252 #endif /* !HAVE_POSIX_SIGNALS */
 253
 254   termsigs_initialized = 1;
 255 }
 256
 257 static void
 258 initialize_shell_signals ()
 259 {
 260   if (interactive)
 261     initialize_terminating_signals ();
 262
 263 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
 264   /* All shells use the signal mask they inherit, and pass it along
 265      to child processes.  Children will never block SIGCHLD, though. */
 266   sigemptyset (&top_level_mask);
 267   sigprocmask (SIG_BLOCK, (sigset_t *)NULL, &top_level_mask);
 268   sigdelset (&top_level_mask, SIGCHLD);
 269 #endif /* JOB_CONTROL || HAVE_POSIX_SIGNALS */
 270
 271   /* And, some signals that are specifically ignored by the shell. */
 272   set_signal_handler (SIGQUIT, SIG_IGN);
 273
 274   if (interactive)
 275     {
 276       set_signal_handler (SIGINT, sigint_sighandler);
 277       set_signal_handler (SIGTERM, SIG_IGN);
 278     }
 279 }
 280
 281 void
 282 reset_terminating_signals ()
 283 {
 284   register int i;
 285 #if defined (HAVE_POSIX_SIGNALS)
 286   struct sigaction act;
 287 #endif
 288
 289   if (termsigs_initialized == 0)
 290     return;
 291
 292 #if defined (HAVE_POSIX_SIGNALS)
 293   act.sa_flags = 0;
 294   sigemptyset (&act.sa_mask);
 295   for (i = 0; i < TERMSIGS_LENGTH; i++)
 296     {
 297       /* Skip a signal if it's trapped or handled specially, because the
 298          trap code will restore the correct value. */
 299       if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
 300         continue;
 301
 302       act.sa_handler = XHANDLER (i);
 303       sigaction (XSIG (i), &act, (struct sigaction *) NULL);
 304     }
 305 #else /* !HAVE_POSIX_SIGNALS */
 306   for (i = 0; i < TERMSIGS_LENGTH; i++)
 307     {
 308       if (signal_is_trapped (XSIG (i)) || signal_is_special (XSIG (i)))
 309         continue;
 310
 311       signal (XSIG (i), XHANDLER (i));
 312     }
 313 #endif /* !HAVE_POSIX_SIGNALS */
 314 }
 315 #undef XSIG
 316 #undef XHANDLER
 317
 318 /* What to do when we've been interrupted, and it is safe to handle it. */
 319 void
 320 throw_to_top_level ()
 321 {
 322   int print_newline = 0;
 323
 324   if (interrupt_state)
 325     {
 326       print_newline = 1;
 327       DELINTERRUPT;
 328     }
 329
 330   if (interrupt_state)
 331     return;
 332
 333   last_command_exit_value |= 128;
 334
 335   /* Run any traps set on SIGINT. */
 336   run_interrupt_trap ();
 337
 338   /* Cleanup string parser environment. */
 339   while (parse_and_execute_level)
 340     parse_and_execute_cleanup ();
 341
 342 #if defined (JOB_CONTROL)
 343   give_terminal_to (shell_pgrp);
 344 #endif /* JOB_CONTROL */
 345
 346 #if defined (JOB_CONTROL) || defined (HAVE_POSIX_SIGNALS)
 347   /* This should not be necessary on systems using sigsetjmp/siglongjmp. */
 348   sigprocmask (SIG_SETMASK, &top_level_mask, (sigset_t *)NULL);
 349 #endif
 350
 351   reset_parser ();
 352
 353 #if defined (READLINE)
 354   if (interactive)
 355     bashline_reinitialize ();
 356 #endif /* READLINE */
 357
 358 #if defined (PROCESS_SUBSTITUTION)
 359   unlink_fifo_list ();
 360 #endif /* PROCESS_SUBSTITUTION */
 361
 362   run_unwind_protects ();
 363   loop_level = continuing = breaking = 0;
 364   return_catch_flag = 0;
 365
 366   if (interactive && print_newline)
 367     {
 368       fflush (stdout);
 369       fprintf (stderr, "\n");
 370       fflush (stderr);
 371     }
 372
 373   /* An interrupted `wait' command in a script does not exit the script. */
 374   if (interactive || (interactive_shell && !shell_initialized) ||
 375       (print_newline && signal_is_trapped (SIGINT)))
 376     jump_to_top_level (DISCARD);
 377   else
 378     jump_to_top_level (EXITPROG);
 379 }
 380
 381 /* This is just here to isolate the longjmp calls. */
 382 void
 383 jump_to_top_level (value)
 384      int value;
 385 {
 386   longjmp (top_level, value);
 387 }
 388
 389 sighandler
 390 termination_unwind_protect (sig)
 391      int sig;
 392 {
 393   if (sig == SIGINT && signal_is_trapped (SIGINT))
 394     run_interrupt_trap ();
 395
 396 #if defined (HISTORY)
 397   if (interactive_shell && sig != SIGABRT)
 398     maybe_save_shell_history ();
 399 #endif /* HISTORY */
 400
 401 #if defined (JOB_CONTROL)
 402   if (interactive && sig == SIGHUP)
 403     hangup_all_jobs ();
 404   end_job_control ();
 405 #endif /* JOB_CONTROL */
 406
 407 #if defined (PROCESS_SUBSTITUTION)
 408   unlink_fifo_list ();
 409 #endif /* PROCESS_SUBSTITUTION */
 410
 411   run_exit_trap ();
 412   set_signal_handler (sig, SIG_DFL);
 413   kill (getpid (), sig);
 414
 415   SIGRETURN (0);
 416 }
 417
 418 /* What we really do when SIGINT occurs. */
 419 sighandler
 420 sigint_sighandler (sig)
 421      int sig;
 422 {
 423 #if defined (MUST_REINSTALL_SIGHANDLERS)
 424   signal (sig, sigint_sighandler);
 425 #endif
 426
 427   /* interrupt_state needs to be set for the stack of interrupts to work
 428      right.  Should it be set unconditionally? */
 429   if (interrupt_state == 0)
 430     ADDINTERRUPT;
 431
 432   if (interrupt_immediately)
 433     {
 434       interrupt_immediately = 0;
 435       throw_to_top_level ();
 436     }
 437
 438   SIGRETURN (0);
 439 }
 440
 441 /* Signal functions used by the rest of the code. */
 442 #if !defined (HAVE_POSIX_SIGNALS)
 443
 444 #if defined (JOB_CONTROL)
 445 /* Perform OPERATION on NEWSET, perhaps leaving information in OLDSET. */
 446 sigprocmask (operation, newset, oldset)
 447      int operation, *newset, *oldset;
 448 {
 449   int old, new;
 450
 451   if (newset)
 452     new = *newset;
 453   else
 454     new = 0;
 455
 456   switch (operation)
 457     {
 458     case SIG_BLOCK:
 459       old = sigblock (new);
 460       break;
 461
 462     case SIG_SETMASK:
 463       sigsetmask (new);
 464       break;
 465
 466     default:
 467       internal_error ("Bad code in sig.c: sigprocmask");
 468     }
 469
 470   if (oldset)
 471     *oldset = old;
 472 }
 473 #endif /* JOB_CONTROL */
 474
 475 #else
 476
 477 #if !defined (SA_INTERRUPT)
 478 #  define SA_INTERRUPT 0
 479 #endif
 480
 481 #if !defined (SA_RESTART)
 482 #  define SA_RESTART 0
 483 #endif
 484
 485 SigHandler *
 486 set_signal_handler (sig, handler)
 487      int sig;
 488      SigHandler *handler;
 489 {
 490   struct sigaction act, oact;
 491
 492   act.sa_handler = handler;
 493   act.sa_flags = 0;
 494 #if 0
 495   if (sig == SIGALRM)
 496     act.sa_flags |= SA_INTERRUPT;       /* XXX */
 497   else
 498     act.sa_flags |= SA_RESTART;         /* XXX */
 499 #endif
 500   sigemptyset (&act.sa_mask);
 501   sigemptyset (&oact.sa_mask);
 502   sigaction (sig, &act, &oact);
 503   return (oact.sa_handler);
 504 }
 505 #endif /* HAVE_POSIX_SIGNALS */